Effects of low levels of ultraviolet radiation on antioxidant mechanisms of Japanese Medaka (Oryzias latipes)

Ultraviolet-B radiation stress alters the competitive outcome of algae: Based on analyzing population dynamics and photosynthesis

The solar ultraviolet-B radiation (UVB) is increasingly affecting the aquatic ecosystems due to the long-term antropic damage to the stratospheric ozone. The distrupted interspecies competition is one of the primary causes driving the plankton community composition shifts under UVB stress. To reveal the competitive responses to enhanced UVB radiation, we grew two green algae Scenedesmus obliquus and Chlorella pyrenoidosa, and the unicellular cyanobacterium Microcystis aeruginosa in monocultures and in cocultures under differerent UVB intensities (0, 0.3 and 0.7 W m^-2), respectively. Results showed that elevated UVB radiation consistently decreased the population carrying capacies and the photosynthesis of the three species in monocultures. While cocultivated, C. pyrenoidosa was competively excluded by the presence of S. obliquus, and the competitive outcome was not affected by UVB exposure. By contrast, unicellular M. aeruginosa overwhelmingly suppressed the population growth of S. obliquus under no UVB, yet S. obliquus tended to be a better competitor under 0.3-0.7 W m^-2 UVB exposure. The species-specific photosynthesis sensitivity to UVB can partly explain the different tolerance of the algae to UVB and the change of competition outcome under elevated UVB. The present study elucidated the potential role of increased UVB radiation in determining the competitions between phytoplankton species, contributing to the understanding of phytoplankton community shifts under enhanced UVB stress.

Exploring the effect of UV-C radiation on earthworm and understanding its genomic integrity in the context of H2AX expression

Maintaining genomic stability is inevitable for organism survival and it is challenged by mutagenic agents, which include ultraviolet (UV) radiation. Whenever DNA damage occurs, it is sensed by DNA-repairing proteins and thereby performing the DNA-repair mechanism. Specifically, in response to DNA damage, H2AX is a key protein involved in initiating the DNA-repair processes. In this present study, we investigate the effect of UV-C on earthworm, Perionyx excavatus and analyzed the DNA-damage response. Briefly, we expose the worms to different doses of UV-C and find that worms are highly sensitive to UV-C. As a primary response, earthworms produce coelomic fluid followed by autotomy. However, tissue inflammation followed by death is observed when we expose worm to increased doses of UV-C. In particular, UV-C promotes damages in skin layers and on the contrary, it mediates the chloragogen and epithelial outgrowth in intestinal tissues. Furthermore, UV-C promotes DNA damages followed by upregulation of H2AX on dose-dependent manner. Our finding confirms DNA damage caused by UV-C is directly proportional to the expression of H2AX. In short, we conclude that H2AX is present in the invertebrate earthworm, which plays an evolutionarily conserved role in DNA damage event as like that in higher animals.

Text message reminders for improving sun protection habits: A systematic review

Background

Excessive exposure to ultraviolet radiation increases the risk of skin cancer and other conditions. SMS text reminders may be a useful tool to improve sun protection habits due to its massive reach, low cost, and accessibility.

Objective

To perform a systematic review of randomized controlled trials (RCTs) that evaluated the effects of SMS text reminders in promoting sun protection habits.

Methods

We performed a systematic search in PubMed, Central Cochrane Library, and Scopus; following the PRISMA recommendations to perform systematic reviews. We included RCTs published up to December 2018, which evaluated the benefits and harms of SMS text reminders to improve sun protection habits. Random-effects meta-analyses were performed whenever possible. The certainty of the evidence was assessed for RCTs estimates using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. The study protocol was registered in PROSPERO (CRD42018091661).

Results

Five RCTs were included in this review. When pooled, the studies found no effect of SMS text reminders in “sunburn anytime during follow-up” (two studies, risk ratio: 0.93; 95% confidence interval: 0.83–1.05). Contradictory results were obtained for sunscreen use (three RCTs) and sun protection habits (two RCTs), however, they could not be meta-analyzed because outcomes were measured differently across studies. The certainty of the evidence was very low for these three outcomes according to GRADE methodology.

Conclusions

RCTs that assessed effects of SMS text reminders did not find a significant benefit on objective outcomes, such as having a sunburn, sunscreen use and composite score of sun protection habits. Since certainty of the evidence was very low, future high-quality studies are needed to reach a conclusion regarding the balance of desirable and undesirable outcomes.

Protocol registration number

PROSPERO (CRD42018091661).

Toxic effects of fluridone on early developmental stages of Japanese Medaka (Oryzias latipes)

The herbicide fluridone is intensively applied to control invasive aquatic plants globally, including in the Sacramento and San Joaquin Delta (the Delta), California, USA. Our previous study revealed that the adult stage of Delta Smelt showed acute and sub-lethal adverse effects following 6 h of exposure to environmentally relevant concentrations of fluridone. To further investigate mechanisms of toxicity of fluridone and to assess its toxicity to early life stages of fish, we performed additional exposures using the fish model Japanese Medaka (Oryzias latipes). Male and female Medaka embryos were exposed to concentrations of fluridone for 14 d and showed reduced hatching success in a dose dependent manner. The half maximal effective concentration for the hatching success was 2.3 mg L^-1. In addition, male and female Medaka larvae were acute exposed to fluridone for 6 h to assess their swimming behavior and gene expression patterns. Fish exposed to fluridone at 4.2 mg L^-1 or higher became lethargic and showed abnormal swimming behavior. The response to the stimuli was significantly impaired by fluridone at 21 mg L^-1 and above in males, and at 104 mg L^-1 in females. Transcriptome analysis identified a total of 799 genes that were significantly differentially expressed, comprising 555 up-regulated and 244 down-regulated genes in males exposed to 21 mg L^-1 of fluridone. The gene set enrichment analysis indicated a number of biological processes altered by fluridone. Among the genes involved in those biological processes, the expression of the genes, acetylcholinesterase, retinoic acid receptor, insulin receptor substrate, glutathione reductase, and glutathione S transferase, exhibited dose- and sex-dependent responses to fluridone. The study indicated that fluridone exposure led to detrimental toxic effects at early developmental stages of fish, by disturbing the biological processes of growth and development, and the nervous system, inducing oxidative stress and endocrine disruption.